Several appliances utilize liquid dispensers. For example, stand alone beverage dispensers and refrigerators may include built-in beverage dispensers. Washing machines, hand soap dispensers and dishwashers may also utilize liquid dispensers to dispense liquid detergents. A class of flexible containers that contain consumables such as flavorant, beverage concentrate, or chemicals such as detergents or soaps have a pump mechanism built into them. The pump mechanism is actuated by an actuator, typically a solenoid, situated on the host appliance. Alternatively, the collapsible containers may include only a built-in valve that is actuated to allow liquid to flow out under the force of gravity or squeezing force applied to the collapsible container. United States Patent Publication No. US2006/0016347 to Girard et al. shows an appliance that includes a collapsible container attached to a pump for providing flavorant to a beverage.
When using such a collapsible container containing a liquid consumable, it can be desirable to know the amount of liquid remaining within the container. Furthermore, between uses, an outlet valve on the container can stick or clog, as residue from the dispensed liquid within the bag dries out and solidifies.